Electronic clocking circuits (hereinafter “clocking circuits”) are used in a wide variety of applications. For example, many solid state electronic devices (e.g., microprocessors) operate at a rate set by an internal or external clocking circuit. Accordingly, the accuracy of the clocking signal generated by a clocking circuit generally is critical to the proper operation of the underlying device being clocked. Many devices thus use conventional crystal oscillators to clock their underlying processes.
Crystal oscillators have a number of drawbacks. Among others, crystal oscillators typically are relatively large and expensive. Consequently, noncrystal clocking circuits have been developed to provide the same function while crystal being both smaller and less expensive. One problem with conventional non clocking circuits, however, is their susceptibility to malfunctioning in extreme environments. Another problem is their processing variability.
More particularly, due to their widespread use, clocking circuits are deployed in a broad array of different environments. For example, outdoor electric meters (for determining the amount of electricity consumed by a house) sometimes have clocking circuits. Clocking circuits in such environments can be subjected to a wide range of temperatures. Typical temperatures can range from 10 degrees below zero F. (e.g., Alaska) to 120 degrees F (e.g., Arizona). In some parts of the world, temperatures can even exceed these temperatures, or range across this entire spectrum during a four season period.
Properties of components within clocking circuits often change when subjected to varying temperature extremes. For example, varying temperatures can affect 1) the capacitance values of capacitors, 2) input and reference voltages, and 3) various thresholds. Such changes can cause the clocking circuit to deliver a varying output clocking frequency, thus causing the device being clocked to operate improperly.